Rubber derivative



Patented Aug. 1, 1939 RUBBER;DERIVATIVE 7 Benjamin 'S. Garvey, Akron,Ohio," assignor" to v The B. F. Goodrich Company, New'York, N.Y.,

a corporation ofNew York No Drawing. Application May 26, 193 I Serial.No. 8 1,813 .51

3" Claims. (01. 260-771) This invention relates to the production ofderivatives of rubber and has for its object the preparation of stable,chemically resistant materials suitable for the preparation of paints,molding plastics, and so forth.

I have found that the treatment of rubber with substantially anhydroushydrogen fluoride yields more or less hard, thermoplastic products whosesolubility depends on the conditions under which they are prepared. Whenmade under suitable conditions, a product is formed which is verysoluble in the usual rubber solvents and is resistant to thermaldecomposition and the action of most chemicals. The types of productobtained are illustrated in the 7 following examples:

Example 1.-Tubes of soft vulcanized rubber are exposed to the vapors ofsubstantially anhydrous hydrogen fluoride. The tubes become hard andrigid.

Example 2.--A piece of unvulcanized crepe rubber is immersed for severalhours in liquid, anhydrous hydrogen fluoride. The hydrogen fluoride isthen allowed to evaporate. The product is hard and brittle.

Example 3.-Hydrogen fluoride gas is passed into 500 cc. of a gasolinesolution containing 25 g. of well masticated rubber. In about 25 minutesthe cement gels. This gel is broken up and soaked in acetone to removethe solvent. The product is horny and insoluble in all of the commonsolvents. On the other hand, the products obtained by precipitation fromthe cement before it gels are not sensibly different from the rubberused as a starting material.

Example 4.-Hydrogen fluoride gas is passed into 500 cc. of a p-cymenesolution containing 25 g. of well masticated rubber. The temperaturerises considerably. In 15 to 20 minutes some 15 to 18 or 20 g. ofhydrogen fluoride are absorbed and absorption of gas practically stops.The clear, reddish solution is allowed to stand a few hours and is thenpoured into two liters of acetone. The product is precipitated from theturbid solution by the addition of about 10 cc. of concentratedhydrochloric acid. It is filtered, washed with acetone, and air dried.The product is a fine white powder readily soluble in gasoline,

benzene, and chlorinated hydrocarbons.

Example 5.-Five liters of a benzene solution containing 250 g. of wellmasticated rubber are put into a copper container equipped with avigorous stirrer, an inlet tube for hydrogen fluoride gas, a vent, astop-cock for drawing off samples of cement and a large outlet for rapidemptying of the cement. The agitator is started and hydrogen fluoridegas is bubbled in rapidly. Small samples are drawn off periodicallythrough the small stop-cock and examined. The solution at once begins toget warm. In about 5 minutes the viscosity drops considerably and after7 or 8 minutes it is almost as low as that of pure benzene. Accompanyingthis change in viscosity is a color change from yellow through orange tored. When the solution becomes orange and the viscosity is at a minimum,the whole charge is dumped as fast as possible into 25 liters of.acetone acidified with 100 cc. of concentrated hydrochloric acid. Theacetone is vigorously agitated. Al fine white precipitate forms whichfilters readily. When washed in acetone and dried the product is a linewhite powder readily soluble in hydrocarbon and ch10- rinated solvents.

If the charge is dumped too soon the product is gummy. If dumped alittle too late the product appears to be satisfactory until attemptsare made to dissolve it when it is found to be only partly soluble. Ifthe charge is not dumped at this stage it soon gels, and if this gelledmaterial. is recovered it is found to be insoluble in all of the usualsolvents.

While acetone has been used as the precipitant in these examples othernon-solvents such as alcohol can be used. 7

Analysis of the soluble product shows the presence of about 3.75%fluorine, whereas the theoretical value a product of the empiricalcomposition for csHal-lF is 19.4% fluorine. However, this product can beobtained only by the use of quantities of hydrogen fluoride much largerthan would be indicated by these results. The preferred hard product isproduced by the addition of at least one mole and preferably 1.5 to 2.5moles of. anhydrous hydrogen fluoride for each theoretical isoprene unitof the rubber. The material has an iodine number of which shows about20% of the unsaturation of rubber. These results indicate that theproduct is partly a hydrogen fluoride addition product and partly acyclorubber, that is, an isomer of rubber. It is a hard, brittlematerial which gives films resembling those from unplasticizednitrocellulose. The

product is generally thermoplastic and if desired can be rendered moreplastic and more easily soluble by mechanical working.

When suitably plasticized and pigmented the product gives excellentlacquers which age well and are resistant to acids, alkalies, and salts.Its

siderably retards the desired reaction. v j

The term rubber when used in theclaimsand specification is intended toinclude caoutchouc,

gutta percha, balata, andsynthetic, rubbers .de

rived from butadiene or sub'stituted ,butadienes in the unvulcanized,vulcanized, or reclaimed condition.

This application is a continuation in part of December my applicationSerial No. 53,105 filed 5, 1935.

I claim:

1. Process for the preparation of thermoplastic compositions whichcomprises isomerizing rubber dissolved in an inert organic solventtherefor by bringing the solution in contact with from 1.5 to 2.5 molesof anhydrous hydrofluoric acid (as such) per isoprene unit of therubber.

2. Process for the preparation of thermoplastic compositions whichcomprises isomeri'zing rubber dissolved in an aromatic hydrocarbonsolvent by bringing the solution in contact with at least one mole ofanhydrous hydrofluoric acid (as such) per isoprene unit of the rubber.

3. .Process for the preparation of thermoplastic compositions whichcomprises isomerizing rubber dissolved in an aromatic hydrocarbonsolvent by contactwith from 1.5 to 2.5 moles of anhydrous hydrofluoricacid (as such) per isoprene'unit of the rubber.

BENJAMIN s. GARVEY. 20

